function quickSort (arr) {
    if (arr.length <= 1) {return arr}
    var pivotIndex = Math.floor(arr.length / 2)
    var pivot = arr.splice(pivotIndex, 1)[0];
    var left = []
    var right = []
    for (var i = 0; i < arr.length; i++ ) {
      if (arr[i] <pivot) {
      left.push(arr[i])
    } else {
      right.push(arr[i])
    }}
    return quickSort(left).concat([pivot], quickSort(right))

}